Semiconductor laser array stacks are known as laser elements with high output. Examples of semiconductor laser array stacks are disclosed in Japanese Laid-Open Publication No. 9-181376 and Japanese Laid-Open Publication No. 2002-9385.
FIG. 2 is a perspective view showing an example of a semiconductor laser array stack. FIG. 3 is a diagram showing a front end surface (light-outputting surface) of a semiconductor laser array. As shown in FIG. 2, a semiconductor laser array stack 12 has a structure wherein a plurality of semiconductor laser arrays 11 and a plurality of heat sinks 13 are positioned alternately. Heat sinks 13 cool laser arrays 11. As shown in FIG. 3, in each semiconductor laser array 11, a plurality of active layers 14 are aligned in parallel in the horizontal direction.
In laser array stack 12, due to laser arrays 11 being layered in the vertical direction, the plurality of active layers 14 are positioned in a matrix-like manner. Each active layer 14 emits laser light. The laser light emitted from these active layers 14 form a single beam. By positioning active layers 14 at a high density, a beam with high optical density is obtained. However in recent years, further improvement of the optical density is being desired.